Valve timing control system for internal combustion engine

ABSTRACT

A valve timing system for an internal combustion engine includes a phase alteration mechanism interposed between a driving rotator and a driven rotator and having a direction turning point at which the phase alteration direction is reversed when a movable portion of the mechanism travels from a beginning to a termination, and an operation control device for displacing the movable portion when undergoing an energization control, the movable portion being displaced toward the beginning when the energization control fails to be carried out. The rotation phase is set at a middle position between a maximum retard position and a maximum advance position when the movable portion is located at the beginning.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/011,061, filed Dec. 15, 2004, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a valve timing control system for aninternal combustion engine, which variably controls the opening/closingtiming of an engine valve in accordance with the engine operatingconditions.

Typically, the valve timing control system comprises a housing rotatedby power of a crankshaft and a camshaft-side shaft member coaxiallymounted thereto, wherein the mounting angle (rotation phase) between thetwo can be adjusted through links and a lever. Specifically, the housingis formed with radial grooves in which respective movable guides of thelinks arranged at distal ends are slidably engaged. A base end of eachlink is rotatably coupled to the lever protrusively provided to theshaft member. An operating rotator is disposed in front of the housingand the shaft member to be rotatable relative thereto. The backside ofthe operating rotator is formed with a spiral groove in which themovable guides of the links are engaged. The operating rotator is biasedby a power spring in the engine rotating direction, and is subjected toa braking force of an electromagnetic brake as required, wherein therelative rotated position of the operating rotator with respect to thehousing can be controlled by controlling energization of theelectromagnetic brake.

With the valve timing control system, when the electromagnetic brake isnot energized, the operating rotator is biased toward the most forwardposition in the engine rotating direction by the power spring, havingthe movable guides operated at a radially inside or outside end of thespiral groove. As a result, the housing and the shaft member are held atthe maximum retard phase or the maximum advance phase through the links.Then, when the electromagnetic brake is energized, the operating rotatoris operated in accordance with the balance between a biasing force ofthe power spring and a braking force of the electromagnetic brake,having the movable guides displaced radially while being guided by thespiral groove, thus adjusting the rotation phase between the housing andthe shaft member through the links. The spiral of the spiral groove isformed to have the diameter reducing continuously from one end toanother end.

SUMMARY OF THE INVENTION

The typical valve timing control system is constructed so that theoperating rotator is operated in accordance with the balance between abiasing force of the power spring and a braking force of theelectromagnetic brake. However, the spiral of the spiral groove isformed to have the diameter reducing continuously from one end toanother end, so that when the electromagnetic brake is turned off, whichoccurs at engine start or standstill, for example, the operating rotatoris biased in one direction by a biasing force of the power spring only,having the movable guides moved up to the radially outside or inside endalong the spiral of the spiral groove. Since movement of the movableguides up to the radially outside or inside end is involved in returningof the rotation phase between the housing and the shaft member up to themaximum retard position or the maximum advance position, the rotationphase which allows engine start should inevitably be set at a positionin the vicinity of the maximum retard position or the maximum advanceposition. Specifically, if the rotation phase which allows engine startis set at a middle position between the maximum retard position and themaximum advance position, engine restart cannot be carried out smoothlydue to impossible natural returning of the rotation phase to the middleposition at engine start or during inertia rotation after engine stop.Thus, the typical valve timing control system does not allow, duringengine operation, effective use of the phase area shifted to the moreadvanced or retardant position with respect to the rotation phase whichallows engine start.

It is, therefore, an object of the present invention to provide a valvetiming control system for an internal combustion engine, which allows,during engine operation, effective use of the phase area shifted to themore advanced or retardant position with respect to the rotation phasewhich allows engine start.

Generally, the present invention provides a system for controlling avalve timing for an internal combustion engine, which comprises: adriving rotator which is rotated by a crankshaft of the engine; a drivenrotator which follows the driving rotator, the driven rotator causingrotation transmitted to a camshaft; a phase alteration mechanisminterposed between the driving rotator and the driven rotator, the phasealteration mechanism comprising a movable portion, the movable portiontraveling between a beginning and a termination to cause relativerotation between the driving rotator and the driven rotator, the phasealteration mechanism having a direction turning point at which a phasealteration direction is reversed when the movable portion travels fromthe beginning to the termination; and an operation control device whichdisplaces the movable portion of the phase alteration mechanism whenundergoing an energization control, the movable portion being displacedtoward the beginning when the energization control fails to be carriedout, wherein a rotation phase is set at a middle position between amaximum retard position and a maximum advance position when the movableportion is located at the beginning.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects and features of the present invention will becomeapparent from the following description with reference to theaccompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view showing an embodiment of a valvetiming control system for an internal combustion engine according to thepresent invention;

FIG. 2 is a schematic front view showing operation of links at themiddle phase when no control is carried out;

FIG. 3 is a view similar to FIG. 2, showing operation of the links atthe maximum retard phase;

FIG. 4 is a view similar to FIG. 3, showing operation of the links atthe maximum advance phase; and

FIG. 5 is a graph illustrating the relationship between the rotationangle of an operating rotator, the diameter of a spiral groove, and thecam phase.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, a description will be made about a preferredembodiment of a valve timing control system for an internal combustionengine according to the present invention. In the illustrativeembodiment, the present invention is applied to an intake-side valveactuating system. Optionally, the present invention can be applied to anexhaust-side valve actuating system.

Referring to FIG. 1, the valve timing control system is disposed at afront end of a camshaft, not shown, rotatably supported on a cylinderhead of the engine, and comprises a driving ring (driving rotator) 2including at the outer periphery a timing sprocket 1 linked to acrankshaft, not shown, a driven shaft member (driven rotator) 4integrally coupled to the front end of the camshaft and for relativelyrotatably supporting driving ring 2 through the base-side outerperiphery, a phase alteration mechanism 5 disposed in front of (on theleft side of) driving ring 2 for operating the mounting angle betweendriving ring 2 and driven shaft member 4, an operation control means ordevice 3 disposed in front of phase alteration mechanism 5 and forcontrolling mechanism 5 in accordance with the engine operatingconditions, and a VTC cover 50 attached to an engine block and forcovering the front faces of the above components and their perimeters.

The intake-side rotation phase of the engine is arbitrarily controlledby the valve timing control system, wherein the rotation phase whichallows engine start is set at a predetermined middle position betweenthe maximum retard position and the maximum advance position.

Driving ring 2 is formed with a stepped insertion hole 2 a which isrotatably engaged with the base-side outer periphery of driven shaftmember 4. Referring particularly to FIG. 2, the front-end face ofdriving ring 2 has two radial grooves (radial guide) 11 formed to beaxisymmetric and extend roughly radially.

Driven shaft member 4 has an increased diameter portion formed at thebase-side outer periphery which abuts on the front end of the camshaft,and two levers 12 integrally formed wit the outer peripheral surface infront of the increased diameter portion to protrude radially. A link 13has a base end rotatably supported to each lever 12 through a pin, and adistal end integrally formed with a cylindrical protrusion 14 whichslidably engages in corresponding radial groove 11.

Link 13 is swingably coupled to driven shaft member 4 with protrusion 14engaging in corresponding radial groove 11. Thus, when the distal end oflink 13 moves along radial groove 11 under an external force, drivingring 2 and driven shaft member 4 are rotated relative to each other bythe action of link 13 and lever 12 in the direction and by an anglecorresponding displacement of protrusion 14.

The distal end of link 13 is formed with an accommodation hole whichopens to the axially front side. Accommodated therein are an engagementpin 16 engaged in a spiral groove (spiral guide) 18 as will be describedlater, and a coil spring 17 for biasing engagement pin 16 forward (tothe side of spiral groove 18). In the illustrative embodiment, a movableguide which moves while being guided by radial groove 11 and spiralgroove 18 is comprised of protrusion 14 and engagement pin 16 of thedistal end of link 13, coil spring 17, and the like.

On the other hand, a spiral plate (operating rotator) 19 having on thebackside a pair of spiral grooves (spiral guides) 18 of semicircularsection is rotatably supported at a position in front of the protrudingposition of lever 12 of driven shaft member 4. Engagement pin 16 isrollingly guided and engaged in spiral groove 18 of spiral plate 19.

Spiral grooves 18 are formed in spiral plate 19 to be axisymmetric andof the same shape. Referring to FIG. 3, the spiral of spiral groove 18includes an increasing area 18 a in which the spiral diameter increasesand a decreasing area 18 b in which the spiral diameter decreases, whenengagement pin 16 travels from one end to another end. A boundary ofareas 18 a, 18 b constitutes a direction turning point P of the presentinvention. Therefore, when engagement pin 16 travels along the shape ofspiral groove 18 from one end to another end, engagement pin 16 movesradially outward up to direction turning point P, and then movesradially inward up to another end of spiral groove 18. The radialvariation range of increasing area 18 a is set to be smaller than thatof decreasing area 18 b, and a beginning “c” (direction turning point P)and termination “d” of decreasing area 18 b are set as a maximum radialposition and minimum radial position. Beginning “c” of increasing area18 a (one end of spiral groove 18) is disposed offset slightly radiallyoutward with respect to a radially middle position between the maximumradial position and the minimum radial position.

In the illustrative. embodiment, the direction from one end of spiralgroove 18 to another end is set as engine rotating direction R.Therefore, when spiral plate 19 rotates relative to driving ring 2 inthe retard direction with engagement pin 16 engaged in spiral groove 18,the distal end of link 13 moves toward termination “d” of spiral groove18 while being guided by radial groove 11. On the other hand, whenspiral plate 19 rotates in the advance direction, the distal end of link13 moves toward beginning “c” of spiral groove 18.

Phase alteration mechanism 5 is comprised of radial grooves 11 ofdriving ring 2, links 13, protrusions 14, engagement pins 16, levers 12,spiral plate 19, spiral groove 18, and the like. Phase alterationmechanism 5 is constructed such that when operation control means 3provides to spiral plate 19 an operating force in the rotatingdirection, the operating force urges to radially displace the distalends of links 13 through engaged portions of spiral groove 18 andengagement pins 16. Then, a relative torque is provided to driving ring2 and driven shaft member 4 by the action of links 13 and levers 12.FIG. 2 shows a state of phase alteration mechanism 5 at the middle phasewhen no control is carried out, and FIGS. 3 and 4 show states of phasealteration mechanism 5 at the maximum retard phase and the maximumadvance phase, respectively, when control is carried out.

A cylindrical wall 20 is arranged at a front end of driving ring 2 tocover links 13 and the outer periphery of spiral plate 19. A cylindricalsmall-diameter base 19 a is integrally formed with spiral plate 19 toprotrude forward. A power spring (biasing means or device) 6 isaccommodated in a space between cylindrical wall 20 and small-diameterbase 19 a. Power spring 6 has ends caught on small-diameter base 19 aand cylindrical wall 20, respectively, to provide from cylindrical wall20 to spiral plate 19 a biasing force in engine rotating direction R.

A hysteresis brake (electromagnetic actuator) 7 is disposed in front ofspiral plate 19 and power spring 6. Hysteresis brake 7 is controlled inenergization by an electric control unit (ECU), not shown, to provide abraking force to spiral plate 19 as required. Hysteresis brake 7, ECU,and power spring 6 constitute an operation control means or device 3. Inaccordance with a balance with a biasing force of power spring 6 actingon spiral plate 19, hysteresis brake 7 controls the rotation phase ofspiral plate 19 with respect to driving ring 2.

As shown in FIG. 1, hysteresis brake 7 comprises a magnetic inductionmember 22 fixed to VTC cover 50 which is a non-rotary member and havinga pair of peripheral faces opposite to each other across a roughlycylindrical clearance, inner and outer pole teeth, not shown, arrangedon the respective peripheral faces, an electromagnetic coil 23 mountedto magnetic induction member 22 and for generating a magnetic fieldbetween the inner pole teeth and the outer pole teeth in accordance withapplied current, and a bottomed cylindrical braking rotor 24 interposedbetween the inner and outer pole teeth in a non-contact way.Electromagnetic coil 23 is controlled in energization by the ECU.

The inner and outer pole teeth comprise a plurality of pole-teethelements extending axially, respectively, which are disposed offsetcircumferentially with respect to each other. Therefore, whenelectromagnetic coil 23 is energized, a magnetic field is generatedbetween the corresponding pole-teeth elements of the inner and outerpole teeth.

Braking rotor 24 is made of a hysteresis material having magnetichysteresis characteristic. Braking rotor 24 at the inner peripheral edgeis supported by magnetic induction member 22 through a shaft member 25,and is coupled to spiral plate 19 through a rubber bush 26 and acoupling pin 27 to be rotatable together. With hysteresis brake 7,therefore, when a magnetic field is generated between the inner andouter pole teeth by energization of electromagnetic coil 23, brakingrotor 24 undergoes a braking force in accordance with applied current,thus decelerating spiral plate 19.

When hysteresis brake 7 is not controlled in energization, spiral plate19 is urged to move forward in the rotating direction under a force ofpower spring 6 only. As a result, at engine start (cranking) or duringinertia rotation after engine stop, spiral plate 19 is maximallydisplaced forward in the rotation direction. Then, engagement pin 16 ofthe distal end of links 13 is displaced to beginning “c” of increasingarea 18 a over direction turning point P of spiral groove 18 as shown inFIG. 2. Since beginning “c” of increasing area 18 a is the radialposition between the maximum radial position and the minimum radialposition as described above, the rotation phase between driving ring 2and driven shaft member 4 operated through links 13 becomes middleposition which allows engine start.

Therefore, during engine cranking, the rotation phase is maintained atthe middle position which allows engine start, obtaining sure enginestart. Maintaining of the middle phase at engine start is carried outwithout relying on a force of hysteresis brake 7, so that even ifhysteresis brake 7 causes a failure such as disconnection, at leastengine start can be ensured.

After engine start, the ECU starts to carry out phase control.Immediately after engine start, hysteresis brake 7 is energized torotate spiral plate 19 the backward direction so that engagement pin 16of the distal end of link 13 moves into decreasing area 18 b of spiralgroove 18 over direction turning point P. Specifically, spiral plate 19is rotated so that engagement pin 16 moves to the same radial position(point “e” in FIG. 5) in decreasing area 18 b as that of beginning “c”in increasing area 18 a.

Then, when changing the rotation phase therefrom to the retardantposition, current to be applied to hysteresis brake 7 is decreased torotate spiral plate 19 in the forward direction, moving engagement pin16 of the distal end of link 13 toward direction turning point P ofdecreasing area 18 b of spiral groove 18 as shown in FIG. 3. With this,the distal end of link 13 moves radially outward to change the rotationphase between driving ring 2 and driven shaft member 4 to the retardantposition. It is noted that the ECU carries out energization control ofhysteresis brake 7 within the range that engagement pin 16 does not moveover direction turning point P at all times.

When changing the rotation phase to the advanced position, current to beapplied to hysteresis brake 7 is increased to rotate spiral plate 19 inthe backward direction, moving engagement pin 16 of the distal end oflink 13 toward termination “d” of spiral groove 18 as shown in FIG. 4.With this, the distal end of link 13 moves radially inward to change therotation phase between driving ring 2 and driven shaft member 4 to theadvanced position.

When turning off the ignition key at engine stop, energization controlof hysteresis brake 7 is not carried out, so that spiral plate 19 isrotated in the forward direction under a force of power spring 6,returning the rotation phase to the middle position during engineinertia operation. However, a case that the rotation phase does notreturn completely to the middle position can be supposed according tothe situation of engine stop. In the illustrative embodiment, even insuch case, the rotation phase can be returned to the middle position atcranking as described above, obtaining sure engine restart.

As described above, in the illustrative embodiment, the ingenious designof the shape of spiral groove 18 allows the rotation phase to naturallybe returned to the middle position when no control is carried out,obtaining sure engine start in the middle phase without requiring anyaddition of complicated mechanisms. Therefore, the phase area shifted tothe more retardant or advanced position with respect to the middleposition can be used during engine operation. By way of example, duringso-called hot idle where stable combustion is carried out, the intakevalve is closed sufficiently late with respect to the bottom dead centerso as to substantially reduce the compressibility, allowing enhancementin fuel consumption. Moreover, during acceleration in the enginehigh-rotation range, the intake valve is closed sufficiently late toenhance an air supercharging effect, resulting also in enhancement inengine output.

In the illustrative embodiment, the electromagnetic actuator includeshysteresis brake 7. Optionally, the electromagnetic actuator may be africtional contact type electromagnetic brake or an electric motor.Further, in the illustrative embodiment, the biasing means includespower spring 6. Optionally, the biasing means may be other spring meanssuch as torsion coil spring. Still further, in the illustrativeembodiment, power transmission from the crankshaft to driving ring 2 isensured by meshing of the chain and sprocket. Alternatively, powertransmission can be ensured by meshing of the gears or frictionalengagement of the belt and pulleys. Furthermore, in the illustrativeembodiment, the driven rotator includes driven shaft member 4 directlycoupled to the camshaft. Alternatively, the driven rotator may becamshaft itself, and driven shaft member 4 may be linked to the camshaftthrough a gear and the like.

As described above, according to the present invention, at engine startor during inertia rotation after engine stop, the rotation phase cannaturally be returned to the middle position due to guide operation ofthe spiral of the spiral guide, obtaining setting of the rotation phasewhich allows engine start at the middle phase. Therefore, the phase areashifted to the more retardant or advanced position with respect to therotation phase which allows engine start can be used during engineoperation.

Further, according to the present invention, after engine start, themovable guide is immediately urged to move to the position in the areafrom the direction turning point to another or second end, which is thesame in phase as the rotation phase which allows engine start, achievingsmooth and quick phase control after engine start.

Still further, according to the present invention, only need to beconsidered when designing the shape of the spiral guide is motion of thecorresponding link, having the advantage that the shape of the spiralguide can be simplified.

Furthermore, according to the present invention, since the biasingdevice comprises a spring, a stable biasing force can provide to theoperating rotator even with simple structure.

Further, the operating rotator is operated in accordance with a balancebetween a force of the biasing device and a braking force of theelectromagnetic brake, allowing simplified structure as compared withwhen adopting an electric motor or the like as electromagnetic actuator.

Having the present invention in connection with the preferredembodiment, it is noted that the present invention is not limitedthereto, and various changes and modifications can be made withoutdeparting from the scope of the present invention.

The entire teachings of Japanese Patent Application P2003-422267 filedDec. 19, 2003 are hereby incorporated by reference.

1-20. (canceled)
 21. A valve timing apparatus for an internal combustionengine, comprising: a driving rotator that is rotatable by a crankshaftof the engine; a driven rotator that follows the driving rotator andthat transmits rotation to a camshaft; a plate including at least onegroove having a varying diameter; a link that swingably couples thedriving rotator and the driven rotator; and a protrusion that isprovided at the link and moved along the groove, wherein the plate isdriven to rotate such that the protrusion moves along the groove andalso moves radially to cause a relative phase angle between the drivingrotator and the driven rotator.
 22. The valve timing apparatus asclaimed in claim 21, wherein the groove is formed in a spiral shape. 23.The valve timing apparatus as claimed in claim 21, wherein the diameterof the groove changes at a turning point.
 24. The valve timing apparatusas claimed in claim 21, wherein the groove includes a region in whichthe diameter decreases.
 25. The valve timing apparatus as claimed inclaim 21, wherein the groove includes a region in which the diameterincreases.
 26. The valve timing apparatus as claimed in claim 21,wherein the groove includes a region in which the diameter increases anda region in which the diameter decreases.
 27. The valve timing apparatusas claimed in claim 21, wherein the plate is driven by an actuator. 28.The valve timing apparatus as claimed in claim 27, wherein the actuatoris a hysteresis brake.
 29. The valve timing apparatus as claimed inclaim 27, wherein the actuator is an electric motor.
 30. The valvetiming apparatus as claimed in claim 27, wherein the actuator is anelectromagnetic brake.
 31. The valve timing apparatus as claimed inclaim 21, further comprising biasing means for applying a biasing forceto the plate in a predetermined direction.
 32. The valve timingapparatus as claimed in claim 21, further comprising a spring thatapplies a biasing force to the plate in a predetermined direction. 33.The valve timing apparatus as claimed in claim 21, further comprising apower spring that applies a biasing force to the plate in apredetermined direction.
 34. The valve timing apparatus as claimed inclaim 31, wherein, while the plate is not being driven, the plate ispositioned by the biasing force of the biasing means such that theprotrusion is substantially at a position at which the diameter changes.35. The valve timing apparatus as claimed in claim 21, furthercomprising a radial guide that allows the protrusion to move along aradial groove for guiding radial movement.
 36. The valve timingapparatus as claimed in claim 21, wherein the protrusion is anengagement pin that is rollingly engaged in the groove.
 37. The valvetiming apparatus as claimed in claim 21, wherein the protrusion isinserted into a hole or a depression formed in the link.
 38. The valvetiming apparatus as claimed in claim 21, wherein the protrusion includesa spring therein, energized to the groove by the protrusion.
 39. A valvetiming control apparatus for an internal combustion engine, comprising:a driving rotator that is rotatable by a crankshaft of the engine; adriven rotator that follows the driving rotator and transmits rotationto a camshaft; a plate including at least one groove having a varyingdiameter; a link that swingably couples the driving rotator and thedriven rotator; a protrusion that is provided at the link and movedalong the groove; and a drive unit that drives the plate, wherein theplate is rotated such that the protrusion moves along the groove andalso moves radially to cause a relative phase angle between the drivingrotator and the driven rotator.
 40. The valve timing control apparatusas claimed in claim 39, wherein the groove is formed in a spiral shape.41. The valve timing control apparatus as claimed in claim 39, whereinthe diameter of the groove changes at a turning point.
 42. The valvetiming control apparatus as claimed in claim 39, wherein the grooveincludes a region in which the diameter decreases.
 43. The valve timingcontrol apparatus as claimed in claim 39, wherein the groove includes aregion in which the diameter increases.
 44. The valve timing controlapparatus as claimed in claim 39, wherein the groove includes a regionin which the diameter increases and a region in which the diameterdecreases.
 45. The valve timing control apparatus as claimed in claim39, wherein the drive unit that drives the plate is an electromagneticactuator.
 46. The valve timing control apparatus as claimed in claim 39,wherein the drive unit is a hysteresis brake.
 47. The valve timingcontrol apparatus as claimed in claim 39, wherein the drive unit is anelectric motor.
 48. The valve timing control apparatus as claimed inclaim 39, wherein the drive unit is an electromagnetic brake.
 49. Thevalve timing control apparatus as claimed in claim 39, furthercomprising biasing means for applying a biasing force to the plate in apredetermined direction.
 50. The valve timing control apparatus asclaimed in claim 39, further comprising a spring that applies a biasingforce to the plate in a predetermined direction.
 51. The valve timingcontrol apparatus as claimed in claim 39, further comprising a powerspring that applies a biasing force to the plate in a predetermineddirection.
 52. The valve timing control apparatus as claimed in claim50, wherein, while the plate is not being driven, the plate ispositioned by the biasing force of the biasing means such that theprotrusion is substantially in a position at which the diameter changes.53. The valve timing control apparatus as claimed in claim 39, furthercomprising a radial guide that allows the protrusion to move along aradial groove for guiding radial movement.
 54. The valve timing controlapparatus as claimed in claim 39, wherein the protrusion is anengagement pin that is rollingly engaged in the groove.
 55. The valvetiming control apparatus as claimed in claim 39, wherein the protrusionis inserted into a hole or a depression formed in the link.
 56. Thevalve timing control apparatus as claimed in claim 39, wherein theprotrusion includes a spring therein, energized to the groove by theprotrusion.
 57. A valve timing control system for an internal combustionengine, comprising: a driving rotator that is rotatable by a crankshaftof the engine; a driven rotator that follows the driving rotator andtransmits rotation to a camshaft; a plate including at least one groovehaving a varying diameter; a link that swingably couples the drivingrotator and the driven rotator; a protrusion that is provided at thelink and moved along the groove; a drive unit that drives the plate; anda control unit that senses a phase angle as a camshaft angle withrespect to a crank angle and sets a phase angle between the drivingrotator and the driven rotator by driving the drive unit, wherein thedrive unit is driven by a signal from the control unit to rotate theplate such that the protrusion moves along the groove and also movesradially and such that the link provided with the protrusion moves tocause a relative phase angle between the driving rotator and the drivenrotator.
 58. The valve timing control system as claimed in claim 57,wherein the protrusion is an engagement pin that is rollingly engaged inthe groove.
 59. The valve timing control system as claimed in claim 58,wherein the protrusion is inserted into a hole or a depression formed inthe link.
 60. The valve timing control system as claimed in claim 57,wherein the protrusion includes a spring therein, energized to thegroove by the protrusion.